In the same decade when gravitational waves and a neutron star merger have been observed, astronomers have now observed what they believe to be the first detection of a black hole swallowing a neutron star.

Last Wednesday, gravitational wave detectors in Italy and the US, called LIGO and Virgo, detected telltale ripples in space and time, traced to an event that happened 8550 million trillion kilometres away from Earth.

Astronomers are analysing the data from the detection to confirm the size of the two objects that came together to form such cataclysmic ripples, but the event is likely a black hole eating a neutron star.

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Neutron stars are the smallest in the universe, the remnants of supernovae. Their diameters are comparable to the size of a city like Chicago or Atlanta, but they are incredibly dense, with masses bigger than that of our sun.

"We have always thought that there should be binary systems of a black hole and a neutron star circling each other out in space, so if this event is confirmed, it would be the first evidence that such systems do actually exist, and that some of them are spiralling closer and closer and eventually smashing together," Ms Scott said.

If the neutron star is not much smaller in mass than the black hole, the astronomers would expect more orbits to bring them closer together.

This would shred the neutron star, creating electromagnetic signals that can be detected, Ms Scott said. The signal would tell the astronomers about the properties of the star, hinting at their mysterious composition.

But if the masses of the two objects differ, the neutron star would likely be swallowed whole and not emit radiation. Because there hasn't been a signal in the area where the event occurred, the researchers believe this is the scenario that occurred.

Astronomers want to learn the masses of the two objects. An object greater than five times the mass of the sun is considered a black hole. If it's less than three times the mass of the sun, it's a neutron star.

One potential small possibility is that the smaller object could be a very light black hole, Ms Scott said, which would still be an exciting consolation prize.

Earlier this year after the gravitational wave detectors were turned on in April, scientists believe they may have detected the never-before-seen collision of a neutron star and a black hole, a collision between two neutron stars and three potential black hole mergers.

The detectors' observations are being regarded as candidates until further data can confirm them.

If this trifecta is complete, the researchers want to detect more systems, including black holes and neutron stars merging.